Well there is lots of definitions of precarious work. You can get an answer on Wikipedia:
http://en.wikipedia.org/wiki/Precarious_work
An answer that feels more like what you will experience is part time, self employed, seasonal and short contract work.
Unstable income, unstable work and lack of rights or access to them are call common problems facing us when we do precarious work.
Although Many in the media talk about our unstable work, rarely do you hear us talking about our own conditions.
Some commentators such as Guy Standing have said that precarious workers are actually a new class of modern society that they refer to as the “Precariat”.
http://www.guardian.co.uk/commentisfree/video/2011/feb/16/precariat-flexible-labour-market-video
Precarious Workers Group 